Communication between devices within a computer system is typically performed using one or more buses to interconnect the devices. These buses may be dedicated buses coupling two devices or non-dedicated buses that are multiplexed by a number of units and devices (e.g., bus agents). Moreover, buses within a computer system may be dedicated to transferring a specific path of information. For example, the X86 microprocessor architecture developed by Intel Corporation of Santa Clara, Calif. includes a three bus system with address, data and control buses for respectively transferring data, address and control signals.
A vast amount of research and system architecture design is directed to increasing data throughput within computer systems. For many years, a popular method of connecting digital systems was the multi-drop bus. In a multi-drop bus, several modules, usually PC boards, connect to a bus via transceivers in a wiring stub. At any given point in time, one module is authorized to transmit and the other module listens. From an abstract point of view, a multi-drop bus configuration is convenient since the configuration permits any module to communicate with any other module.
Unfortunately, multi-drop buses are rarely used today in high performance digital systems due to the fact that the stubs severely limit the bandwidth at which the bus can operate. In other words, within high performance systems which operate at high frequency clock rates, signals along the bus line are continuously degraded by the presence of each stub connection. As a result, transmission line reflections and consequent inter-symbol interference often occurs when operating at high frequencies. Accordingly, high performance digital systems generally utilize either point-to-point connections for devices in order to avoid the limitations inherent in multi-drop buses.
As a result, the number of system cards that may be attached to the high performance digital system is drastically reduced and generally limited to the attachment of only one card, such as for example, a memory card. The attachment card is generally referred to by those known in the art as a daughter card. In other words, current systems are unable to provide connections for inserting available daughter cards to increasingly high speed mother board memory buses without compromising system performance. As a result, providing daughter cards within conventional systems requires a point-to-point connection for each attached daughter card, including for example, memory cards, I/O cards, video cards and the like.